Rationale

1. Currently, C1861 requires the attachment flanges of external corner reinforcement lathing accessories to be 2-1/2 in. long, minimum. 2. The primary source for C1861 content was C1063 which never contained a dimensional requirement for the attachment flanges of external corner reinforcement lathing accessories. During the development of the requirements for external corner reinforcement accessories, a poll was made of the existing accessories being produced and it had been understood at that time that 2-1/2 in. attachment flanges were what was being produced, so that dimension was added with good intentions, to C1861 from its first edition in 2017. 3. Based on recent information and further review we now understand that at least two major manufacturers have been producing external corner reinforcement lathing accessories for decades with attachment flanges of slightly less than the current 2-1/2 in. requirement. Apparently, these manufacturers were unfortunately overlooked when the 2-1/2 in. dimension was determined for C1861. No negative performance issues are known to occur resulting from these slightly shorter attachment flanges. The tooling that produces these products is of fixed dimension and not adjustable to other dimensions. As an example, one manufacturers’ cornerbead has an attachment flange of 2.3 inches. 4. Additionally, external corner reinforcement lathing accessories are now currently and have been made for many years in a range of special purpose configurations requiring special flange lengths both shorter and longer than 2-1/2 in. such as short flanges for recessed openings, for bullnose corners, and long legs for special uses. The 2-1/2 in. minimum dimension does not reflect all current lathing needs for external corner reinforcement. 5. Finally, the existing 2-1/2 in. attachment flange dimension seems unnecessarily restrictive and does not reflect the decades long history of successful performance of products that have been in service with different attachment flange dimensions.